1. Field of the Invention
This invention relates to pins and more particularly to compliant pins for making mechanical and/or electrical connections.
2. Description of the Prior Art
In the prior art, a pin affixed to a member is used for many different types of applications and affixing a pin to a member is done in a variety of ways. In the electronic packaging art, the pin has a mechanical and/or electrical function. U.S. Pat. No. 4,131,933, assigned to the common assignee herein, and U.S. Pat. No. 4,731,701 are examples of such pins used as electrical connectors that are mountable and pluggable, respectively, in the receptacles of printed circuit boards.
One well known way to affix the pin to a member is to provide the member with an opening and to provide the pin with a compliant section with a compatible size such that the section, when inserted into the opening, coacts with the wall or walls of the opening to maintain the pin affixed to the member. The pins are sometimes referred to in these applications and, in particular, in the electronic packaging art simply as compliant pins, and are generally often used therein as electrical connectors or terminals. Compliant pins provide certain advantages over non-compliant types in that they are generally more easy to install/remove and/or rework.
Typical examples, to name just a few, in the electronic packaging art of a pin affixed to an opening in a member and/or methods for affixing the pin to the opening, sometimes referred to in the art as pinning, are as follows:
Non-compliant pin types: PA0 Compliant pin types:
U.S. Pat. Nos. 2,877,441, 3,028,573, 3,354,854, 4,110,904 4,530,551, 4,548,450 and 4,781,602. PA1 U.S. Pat. Nos. 3,545,080, 3,783,433, 3,880,486, 3,971,610, 4,017,143, 4,057,315, 4,076,356, 4,381,134, 4,475,780, 4,533,204, 4,586,778, 4,701,140, 4,735,575, 4,737,114, 4,743,081, 4,752,250, 4,763,408, and 4,780,958; and the publications entitled "Insulated Pin For Printed Circuit Cards With Feed-Through Holes" and "Compliant Serpentine Contact", IBM Technical Disclosure Bulletin, Vol. 29, No. 3, August 1986, pp 1228-1229, and Vol. 30, No. 12, May 1988, pp 235-236, respectively.
In the non-compliant pin types, the pin is not readily installed or amenable to removal and/or rework as it requires a head and bulge for sandwiching the member therebetween and thus requires the formation of such members either before or after installation which in turn may require removal of the head or bulge and hence the destruction of the pin during subsequent removal or rework of the pin from the member. Also, the head and bulge radially extend outwardly and overlap the surface of the member surrounding the opening. This limits the use and availability of the overlapped surface area of the member, and in applications where the member is a circuitized substrate such as a printed circuit board, for example, takes up valuable real estate on the substrate. In other non-compliant types, as well as certain compliant types, inserting the pin into the opening subjects the wall of the opening to damage and/or destruction of the wall's integrity due to the configuration of the pin, and/or adverse deformation or destruction of the pin itself. Two examples of such configurations are a pin with an elongated slit or a pin with an open cross-section such as, for example, a C-shape. Furthermore, where the wall of the opening is conductive plating and the pin and the plating form an electrical connection at their interface, the damage and/or destruction of the plating detrimentally affects the reliability of the connection. Moreover, the compliant sections of the prior art because of their configurations and/or their propensity to deform adversely affects the reliability of the gas tight seal desired in the interface or contact point of the section and the plating of the wall of the opening. Moreover, as such, the prior art pins are not amenable for use in high density pin arrays and/or micro-miniature size pins and/or openings.
Thus, in the case of the aforementioned non-compliant pin type references, for example, the tubular terminal pin of U.S. Pat. No. 2,877,441 has two opposed skirts that are formed by two longitudinal elongated slots extending from one end of the pin to an intermediate portion of the pin. A bump-like outward projection is formed on each skirt in the intermediate portion. Located and formed on the pin remote from its aforementioned end and intermediate portion is a ring-like projection, i.e. a bead, which acts as a stop. The pin is affixed to a printed circuit board by inserting the skirts into a hole which penetrates the board. A camming action occurs between the hole wall and the two skirts as the pin is being inserted, i.e. passed through the hole, that causes compression of the two skirts towards each other. The spacing between the bead and the two projections is compatible to the thickness of the board so that when the bead is reached further insertion is prevented and the two projections will have cleared the hole. As a result, the skirts return to their normal outwardly expanded positions causing the pin to be locked to the board between its bead and its two projections.
The probe connector of U.S. Pat. No. 3,028,573 has a spring-like conductive member with a U-shape configuration, the two legs of which are outwardly bowed with respect to each other. Insertion of the probe into the aperture of a printed wiring cross-connecting board compresses the legs towards each other and thus retains the probe in the aperture.
The tubular electric contact pin of U.S. Pat. No. 3,354,854 is retained in the hole of a terminal fitting by staking or embedding an end portion of the pin in the terminal fitting.
In U.S. Pat. No. 4,110,904, a pre-headed terminal pin, with spine-like knuckled ridges formed in the insertion end portion of the pin, is inserted in the aperture of a ceramic type substrate so that the flange forming the head abuts the bottom surface of the substrate. The aperture is recessed at the top surface of the substrate and the insertion end portion upset, i.e. swaged, to form a bulge within the recess of the aperture. As a result, the pin terminal is clamped to the substrate between its bulge and head.
The wiring change pin of U.S. Pat. No. 4,530,551 has two threadably engaged parts One part has an externally threaded end which is inserted through and extends outwardly from a plated thru hole of a printed wiring board. The second part has a hollow internally threaded end section for receiving the aforementioned externally threaded end of the first part. A shoulder on the first part and the enlarged end section of the second part provide retention of the pin in the hole when the two are in threaded engagement.
In the pin and collar arrangement of U.S. Pat. No. 4,548,540, a non-compliant pin is rigidly engaged by the bore of the highly conductive elastomer collar, which in turn fits into a plated through hole of a printed circuit board. The collar has a circular configuration or alternatively has a plurality of longitudinal ridges formed on its outer surface.
In U.S. Pat. No. 4,781,602, a non-compliant pin plugs into a cantilever beam spring socket that is filled with a non-conductive elastomer. The socket is fitted into a plated through hole with sufficient clearance for a solder bond to be effected between the plating of the hole wall and the outer surface of the socket.
Referring now to the aforementioned compliant pin type references, in U.S. Pat. No. 3,545,080, compliant pins are formed with resilient sections out of solid stock or bars with U-shape and split shape cross-section configurations, the latter also referred to in the art as eye-of-the-needle, The resilient section are inserted into the conductive plated aperture of printed circuit board for retention therein.
The respective wedging locking sections of the different electrical contact pins of U.S. Pat. No. 3,783,433, have cross-section configurations of simple C-shape, compound C-shape, V-shape, four-leaf-clover shape and split sections
In U.S. Pat. Nos. 3,880,486 and 3,971,610, a resilient elastomer conductor connector element or plug with heads on each of its end is used to retain the element or plug in the hole of a printed circuit board and make contact and electrical connection between the metallized outer surface patterns of the board.
The solderless electrical contact of U.S. Pat. No. 4,017,143 has a C-shaped cross section.
The circuit board pin of U.S. Pat. No. 4,057,315 is solid and has an expanded mounting portions with wedge shaped voids.
The compliant section of the electrical connector of U.S. Pat. No. 4,076,356 has plural pressure ridges formed on its outer surface.
The compliant section of the electrical connector of U.S. Pat. No. 4,381,134 has a C-shaped cross section.
The respective compliant sections of the electrical connectors of U.S. Pat. Nos. 4,475,780 and 4,586,778 have S-shaped cross sections.
In U.S. Pat. No. 4,533,204, the mounting section of an electrical contact is split to form two bowed blade sections, each having a C-shaped cross section.
The compliant portion of the electrical connector of U.S. Pat. No. 4,701,140 has two oppositely disposed C-shaped segments.
The free edges of the spring vanes formed in the compliant mounting section of the contact terminal of U.S. Pat. No. 4,735,575 are made sharp enough to penetrate the plating material of the through hole of a printed circuit board.
In U.S. Pat. No. 4,737,114, the electrical contact pin is split into two legs in the form of an eye-of-the-needle type compliant section.
The compliant section of the connector of U.S. Pat. No. 4,743,081 has a split portion defining two legs. The connector also has a stabilizer section adjacent the compliant section. The stabilizer section or both the stabilizer and compliant section engage the wall of a plated through hole.
The mounting section of the compliant pin of U.S. Patent 4,752,250 is split in two parts, each having a C-shaped cross section.
The compliant section of the connector of U.S. Pat. No. 4,763,408 is formed from solid stock and is split to define two resilient leg members.
In U.S. Pat. No. 4,780,958, a plurality of slits are spaced around the tubular compliant mounting section of a contact terminal, and along one side of each slit are a pair of outward projections to engage the wall of a plated through hole.
Thus, in some of these electronic packaging applications, an electrical conductive compliant pin is affixed by its compliant section in the plated thru hole of a substrate so that the pin extends outwardly from at least one surface of the substrate. The substrate has multilayer circuit patterns and may be a multilayer printed circuit board or a multilayer metallized ceramic substrate. The conductive plated thru hole is connected to one or more of the substrate circuit pattern layers.
In the aforementioned IBM Technical Disclosure Bulletin August 1986 publication, a pin having an enlarged compliant section split in two parts is located in the hole of a printed circuit board and connects the circuits located on the two opposite sides of the board. Also, a non-compliant pin is located in a compression insulator sleeve, which in turn is located in another hole of the board, and is connected to other circuitry.
The serpentine contact of the aforementioned IBM Disclosure Bulletin May 1988 publication is provided with a compliant section tail that has a circular, or C-shaped, cross section that is press fitted into a printed circuit board.